DESCRIPTION OF PLATES. 195 
No. 21. Melosira sulcata. V. Peru- Guano. 
Oe 2 = ee P.V. 
ss 623. Cheetoceras didymum. Peru- Guano. 
‘¢ 24. Dicladia capreolus. Peru- Guano. 
‘¢ 25. Syndendrium diadema. Peru- Guano. 
SECTIONS OF ANIMAL TISSUES. 
The fact that vegetable tissues are built up of 
cells has been amply illustrated in the present vol- 
ume. The same is true of animal tissues, and in 
some of these they may be readily demonstrated, 
as for example, in adipose tissue (Plate XVII. 
Fig. 1). 
In other cases, the cells being much smaller 
and the investing membrane extremely delicate, 
the demonstration can only be made by resorting 
to special methods of preparation, and especially 
to staining processes. Thus the delicate mem- 
brane which lines the blood-vessels appears to be 
homogeneous when examined in water or gly- 
cerine without staining; but the outlines of the 
separate cells of which it is made up are brought 
into view when the preparation is stained with 
nitrate of silver. Again, there may be a wide 
departure from the form of the typical cell, as 
in muscular fibres, which are greatly elongated 
fusiform cells. ; 
A knowledge of the details of animal histology 
and of the various methods of preparing animal 
tissues for microscopical examination may be ob- 
tained from the works of Frey, Beale, Stricker, and 
Satterthwaite, already referred to (pp. 118, 119). 
